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Rick Viola (goodrat)
Username: goodrat

Registered: 05-2011
Posted on Tuesday, November 15, 2011 - 07:41 pm:   

11-15-11 RJV
Current rev is E
-Parallel 2uF/350v across C35 (2uF) for 4uF total
-Changed C33 and C34 (60uF) to 100uF
-Changed R9 (560K) to 100K , leave R10 at 100K.
-Changed R12 (5.1K) to 1.82K
-Changed R11 (330K) to 200K
-Changed R69 (3.3K) to 1.82K
-Changed R61 (47K) to 15K
-Parallel 47pF across R21 (82K)
-Add 150K in series with V2-7 grid
-Note: C48 and C10 are 10uF.
-Changed IC1 to OPA2604
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Rick Viola (goodrat)
Username: goodrat

Registered: 05-2011
Posted on Tuesday, November 15, 2011 - 07:49 pm:   

Sorry double post. I thought the post didn't work due to how far down the list it was. But this is current.
I had a problem with the 12AX7 being microphonic, but a new Electro Harmonix 12AX7EH cleared that up just fine.
Current measurements (I think):
C34 283VDC
C33 565VDC
C35 263VDC, Ripple = 200mV p-p ?
C6 200VDC (63V across R9 = .63mA idle, -1.14vgrid)
PLATE 12AX7 141VDC
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Rick Viola (goodrat)
Username: goodrat

Registered: 05-2011
Posted on Wednesday, November 16, 2011 - 08:39 pm:   

Correction, the plate is 130V and 67V across R9, so idle current is 0.67mA and grid is -1.22.
All other measurements the same.
I must have measured with the 180K Plate resistor.
I think I will leave it this way. Although I wonder about lowering C48 and C10 cathode caps. They were there from previous owner at 10uF.
The dist channel is like the normal until the dist gain is > 3.

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